ci: update Travis CI build matrix

Change-Id: Ibcf09a714ca6552a48c19165b9ebe47b74e8fa6b
diff --git a/.jenkins.d/00-deps.sh b/.jenkins.d/00-deps.sh
index b5671bc..c020871 100755
--- a/.jenkins.d/00-deps.sh
+++ b/.jenkins.d/00-deps.sh
@@ -25,6 +25,6 @@
 
 elif has Ubuntu $NODE_LABELS; then
     sudo apt-get -qq update
-    sudo apt-get -qy install g++ pkg-config python3-minimal \
+    sudo apt-get -qy install build-essential pkg-config python3-minimal \
                              libboost-all-dev libssl-dev libsqlite3-dev
 fi
diff --git a/.travis.yml b/.travis.yml
index 7c63efd..8ff6d27 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,6 +24,7 @@
     - env: COMPILER=clang++-8
     - env: COMPILER=clang++-10
     - env: COMPILER=clang++-11
+    - env: COMPILER=clang++-12
 
     # macOS
     - os: osx
@@ -38,9 +39,15 @@
     - os: osx
       osx_image: xcode11.3
       env: # default compiler
+    - os: osx
+      osx_image: xcode11.6
+      env: # default compiler
+    - os: osx
+      osx_image: xcode12
+      env: # default compiler
 
   allow_failures:
-    - env: COMPILER=clang++-11
+    - env: COMPILER=clang++-12
 
   fast_finish: true
 
@@ -57,7 +64,7 @@
         # https://apt.llvm.org/
         LLVM_REPO=${COMPILER/clang++/llvm-toolchain-${TRAVIS_DIST}}
         travis_retry wget -nv -O - "https://apt.llvm.org/llvm-snapshot.gpg.key" | sudo apt-key add -
-        travis_retry sudo add-apt-repository -y "deb http://apt.llvm.org/${TRAVIS_DIST}/ ${LLVM_REPO%-11} main"
+        travis_retry sudo add-apt-repository -y "deb http://apt.llvm.org/${TRAVIS_DIST}/ ${LLVM_REPO%-12} main"
         travis_retry sudo apt-get -qq update
         ;;
     esac